Democratic Sens. Tim Johnson of South Dakota, Carl Levin of Michigan and Dianne Feinstein of California wrote to Director of National Intelligence James R. Clapper Jr. on Friday, urging him to provide regular briefings on Iran.

The chairmen of the Senate Banking, Armed Services and Intelligence committees, respectively, want Clapper to keep Congress up to date on Iran's compliance with the terms set by Western leaders to curb the nation's nuclear program.

"If the extensive inspection and verification system provided for in the agreement is executed faithfully, this will help to build confidence that, at least in the short term, Iran will be unable to pose a credible military threat to its neighbors in the region, including Israel," the senators wrote.

Read the full letter below.

December 6, 2013

The Honorable James R. Clapper

Director of National Intelligence

Office of the Director of National Intelligence

Washington, DC 20511

Dear Director Clapper:

We are writing to seek the information needed to fulfill our legislative and oversight responsibilities regarding Iran’s nuclear program and the ongoing P5+1 negotiations, and to help us evaluate the interim agreement (the “Joint Plan of Action”) signed in Geneva on November 24, 2013.

First, we request periodic briefings from the Intelligence Community, every 45 days beginning on January 30, 2014, concerning whether Iran is acting consistent with the terms of the interim agreement regarding Iran’s nuclear activities. As you know, the goal of the Joint Plan of Action, as described in its preamble, is “to reach a mutually agreed-upon long-term comprehensive solution that would ensure Iran’s nuclear program will be exclusively peaceful.” In order to reach that goal, the United States and other P5+1 members must have confidence that Iran’s actions are fully consistent with the Joint Plan’s terms and conditions, and ongoing monitoring by the IAEA and the Intelligence Community will be key to that verification.

We would especially appreciate your assessments of whether Iran’s actions are consistent with its obligations with respect to:

(i) Converting or diluting its existing stock of 20 per cent enriched uranium;

(ii) Capping its uranium enrichment for the next six months at five per cent;

(iii) Imposing agreed-upon restrictions on Iran’s activities at the Natanz Fuel Enrichment Plant, the Fordow facility, and the Arak reactor;

(iv) Abiding by all its obligations with respect to enhanced monitoring of its nuclear activities (including centrifuge assembly workshops, rotor production workshops and facilities, and uranium mines and mills) by the IAEA; and

(v) The absence of any covert nuclear facilities at which Iran could conduct nuclear-related work.

If the extensive inspection and verification system provided for in the agreement is executed faithfully, this will help to build confidence that, at least in the short term, Iran will be unable to pose a credible military threat to its neighbors in the region, including Israel.

Second, we request a report by December 12, 2013 on the Intelligence Community’s assessment of the effects, if any, on both Iran and our P5+1 partners, of action by Congress relative to new nuclear-related sanctions on Iran while the negotiations between the P5+1 and Iran are ongoing. This document should, to the extent possible, be public. We understand, however, that it may need to contain a classified annex.